Cold Areas Research Articles

Citizen Observations Shed New Light on Geographic Variation in Colour Polymorphism of a Widespread Reptile

ABSTRACTAimColour polymorphism within ectothermic species and populations is shaped by multiple selection pressures that can vary geographically. Here, we tested different hypotheses to better understand this variation in colour polymorphism. The thermal melanism hypothesis predicts that darker colouration is beneficial in colder regions, due to enhanced heat absorption, while the predation pressure hypothesis predicts that melanistic individuals are exposed to a higher predation risk because they are more visible to predators. Additionally, temperature, land cover and predation pressure could interact to influence colour morph frequencies due to trade‐offs regarding thermoregulation and predation risk.LocationEurasia.TaxonEuropean adder (Vipera berus).MethodsWe compiled a dataset of > 7000 citizen observations across the entire distribution of the European adder, scoring adder colouration to test the above‐mentioned hypotheses concerning geographic variation in colour polymorphism, using Bayesian generalised nonlinear regression models.ResultsWe found support for the thermal melanism hypothesis, with the frequency of melanism increasing in colder regions. Moreover, in colder areas, the proportion of melanistic snakes increased with avian predator density, whereas this pattern was weaker in warmer areas, potentially because melanistic snakes spend less time basking and therefore experience reduced predation rates compared to brown and grey snakes. Finally, we found the proportion of melanistic individuals to decline at higher elevations (> 1000 m), potentially due to increased access to basking opportunities or because higher elevations facilitate easier detection of melanistic snakes by predators.Main ConclusionsCombined, our results emphasise the large potential of citizen observations to obtain novel insights concerning biogeographic patterns of morphological divergence in colouration. Our findings increase the understanding of the underlying mechanisms affecting colour polymorphism in ectothermic animals, providing valuable information to predict how species might respond to global change.

Study on the physical mechanical properties and freeze-thaw resistance of energy storage concrete with artificial phase change aggregate

As the main material for major infrastructure in cold regions, the mechanical properties and freeze-thaw resistance of concrete have become key scientific issues affecting the safety and normal operation and maintenance of infrastructure in cold regions. Energy storage concrete with phase change materials (PCM) has high thermal storage performance, which is beneficial to improving the frost resistance of concrete. In our preliminary research work, the artificial phase change aggregate (APCA) containing PCM with high latent heat, good mechanical properties and frost resistance were made and tested. The APCA was added to the concrete and replaced with natural coarse aggregate in different proportions, resulting in several energy storage concrete schemes with different APCA contents. The water absorption characteristics, microstructure and pore characteristics of energy storage concrete with different APCA contents were tested and analyzed through negative pressure saturation test, SEM and MIP. The effects of APCA replacement on the composition, mechanical properties, failure morphology characteristics and frost resistance durability of energy storage concrete at various ages were analyzed through XRD test, strength test and freeze-thaw cycle test. The results showed that replacing natural coarse aggregates with APCA changed the pore characteristics of concrete, reduced its saturation water absorption rate, but did not change the composition of hydration products at various ages of concrete. Replacing with an appropriate amount of APCA in concrete is beneficial for reducing the total porosity, the number of more-harmful pores and harmful pores. APCA reduce the compressive strength and splitting tensile strength of energy storage concrete at various ages. The early splitting strength of energy storage concrete increases rapidly, while the later growth is relatively slow. APCA are beneficial for suppressing the expansion of pores and cracks under freeze-thaw action of concrete. APCA is helpful to improve the freeze–thaw resistance of the energy storage concrete. After 100 freeze-thaw cycles, their strength is still 96% of the 28 day strength, and their compressive strength is about 35 MPa. This study provides a reliable experimental and theoretical basis for improving the freezing resistance of concrete in cold area.

A Novel Heat Pulse Method in Determining “Effective” Thermal Properties in Frozen Soil

AbstractAccurate and fast measurements of thermal properties are frequently required for characterizing the heat‐water dynamics in frozen soil. Measuring the thermal properties of frozen soil without inducing ice thaw has proven challenging with conventional heat pulse (HP) methods. In this study, based on an Infinite Line Source (ILS) semi‐analytical model that applies a constant temperature lower than the freezing point at the heat source to prevent the initiation of ice thaw in the frozen soil, we propose a novel HP‐based approach to measure thermal properties, applicable at temperatures below or above 0°C. Laboratory experiments and numerical modeling were utilized to validate the applicability of the approach and optimization strategies of the measurement. We found that the proposed HP‐based approach effectively maintained the maximum spatial temperature below the freezing point and therefore estimated the bulk thermal properties of quartz sand and ice contents. An optimized measurement strategy was proposed to monitor the temperature variations 2–4 cm away from the center of the heat probe after 60 s. This progress can largely facilitate the determination of the thermal properties of multi‐phase and ‐component frozen soil such as thermal conductivity, heat flux, and ice content in cold areas across soil science, hydrology, engineering, and climate science.

C-repeat binding factor (CBF) identification and expression pattern to abiotic stress response in Casuarina equisetifolia and overexpression of CeCBF4 increase stress tolerance in Arabidopsis

Casuarina equisetifolia stands out as a highly valuable tree species crucial for industries and ecological restoration projects in tropical and subtropical regions, owing to its exceptional salt resistance. However, its growth is hampered in cold and drought-prone areas. Understanding the genetic basis for abiotic stress tolerance is imperative for enhancing stress-resistant breeding efforts of C. equisetifolia. However, the CBF genes are renowned for their pivotal roles in cold response and broad resilience to other adverse environments, such as drought, and high salinity. In this study, five CeCBFs were identified from the genome of C. equisetifolia. CeCBF1 and CeCBF3 belong to Clade I group, which diverged early from DREBIII members, while CeCBF2, CeCBF4, and CeCBF5 are classified into Clade II, a group innovated from Clade I. These genes lack introns in their sequences. The proteins encoded by CeCBFs feature classic AP2 domains and CBF signature sequences, localize in the nucleus and exhibit transactivation activity. Additionally, stress-related, abscisic acid, and jasmonic acid responsive elements are present on the CeCBFs promoters. Expression analysis revealed that CeCBFs were prodominantly induced by cold, drought, and salinity treatments, except for CeCBF1, which showed repression specifically under low temperature. Moreover, CeCBF1, CeCBF4, and CeCBF5 were inhibited by abscisic acid, while CeCBF1 showed reduced transcript levels in response to methyl jasmonate treatment. Furthermore, overexpression of CeCBF4 enhanced tolerance to low temperature, depriving of water, and salt by up-regulating stress-responsive genes expression and promoting proline accumulation, albeit with a trade-off in growth and productivity. Hence, CeCBFs emerge as potential regulators contributing significantly to stress tolerance mechanisms in C. equisetifolia.

Statistical Evaluation of Uniform Temperature and Thermal Gradients for Composite Girder of Tibet Region Using Meteorological Data

To accurately assess the temperature action and effect of steel-concrete composite girder bridges in plateau and cold areas, this paper investigated nearly 50 years of historical meteorological data from 26 meteorological observation stations in the Tibet region of China. Based on the most unfavorable extreme meteorological data at each meteorological station, a finite element model was used to analyze the temperature field of the composite girder. The most unfavorable values of temperature were obtained. The regional differences in temperature actions at different meteorological stations were analyzed, and the isotherm maps of the extreme values of the uniform temperature and thermal gradients were further obtained based on spatial interpolation methods in the ArcGIS program. The study shows that the uniform temperature is significantly affected by the climatic environment, and the isotherm maps provide a visual representation of the geographic distribution pattern of temperature extremes. The maximum and minimum uniform temperatures in Tibet range from 18.28 °C to 42.27 °C and from −41.07 °C to 4.71 °C respectively. The maximum regional difference of positive and negative thermal gradient reaches 11.32 °C and 7.69 °C respectively. The temperature effects calculated using the most unfavorable values of the isotherm map are all more unfavorable than the specification calculations. In particular, the tensile stress of the concrete under the positive thermal gradient reaches 2.91 MPa, which exceeds the standard value of the tensile strength of concrete. This is a significant risk factor for cracking. The compressive stress of the steel girder under a negative thermal gradient reaches 19.35 MPa, which represents a 136% increase compared to the specified value. This increase elevates the risk of instability in the steel girder.

Research on the Operation Optimization of Public Building Systems in Extremely Cold Areas Based on Flexible Loads

The heating energy consumption in public buildings in cold regions is notably significant, presenting substantial scope for energy savings and emission reductions. Flexible loads can actively participate in controlling the operation of the power grid, improving the energy utilization and the economy of the system. This study introduces flexible loads into the operation optimization of energy systems, establishing mathematical models for flexible thermal and electrical loads. A two-stage operation optimization method is proposed: the first stage simulates the starting and stopping control conditions of equipment at varying temperatures and times, selecting the optimal time period to regulate the thermal loads; the second stage employs a multi-objective particle swarm optimization algorithm to optimize the scheduling of the system’s electrical load. Finally, an empirical analysis is carried out in a public building in Shenyang City as an example, and the results indicate that optimal scheduling of flexible thermal and electrical loads reduces the daily operating cost of the energy supply system by RMB 124.12 and decreases carbon emissions by 22.7%.

Endophytic bacteria in Halogeton glomeratus from mining areas are mainly Sphingomonas pseudosanguinis, with a Cyanobacteria moving from roots to leaves to avoid heavy metals

In the cold and arid mining areas of Northwest China, Halogeton glomeratus C. Meyer (Amaranthaceae) is a promising plant for the remediation of heavy metal pollution. In this study, samples correspond to a gradient of nickel and copper pollution, and this study aims to analyze the characteristics of endophytic bacteria in H. glomeratus under such pollution gradients. Samples of the plant H. glomeratus and their corresponding rhizosphere soil were collected from a smelting area, a mining area, and a control area within the Jinchang mine. In mining and smelting areas, Ni in H. glomeratus rhizosphere soils was 95 and 6 times, and Cu was 40 and 94 times higher than control area. Ni in H. glomeratus from these areas was 27 and 4 times, and Cu was 4.2 and 4.6 times greater than control area. The endophytic bacteria predominantly found in H. glomeratus from nickel-copper mining regions was Sphingomonas pseudosanguinis. Our findings might corroborate the notion that heavy metal stress in the soil can markedly facilitate the migration of an unclassified second most abundant species of Cyanobacteria, residing within the roots of H. glomeratus, to aerial tissues, where the stress from heavy metals was diminished. RDA indicated that the migration and enrichment of nickel and copper into the tissues of H. glomeratus in smelting and mining areas influenced changes in the community structure of endophytic bacteria. Under varying levels of nickel and copper stress, endophytic bacteria underwent alterations in their metabolic characteristics, aiding H. glomeratus in withstanding heavy metal stress through processes such as lipid, nucleotide, and amino acid metabolism, xenobiotics biodegradation and metabolism, protein folding, sorting, and degradation, as well as replication and repair. The identification of plant growth-promoting traits, including the ability to release phosphorus, produce IAA and ACC deaminase, and exhibit tolerance to nickel and copper, among culturable dominant strains, had shown that Pseudomonas oryzihabitans K2l-2-LB and Pseudomonas putida K2r-3-R2A possess significant potential for application. These strains could be effectively utilized as microbial inoculants to promote plant growth during the restoration of vegetation in nickel and copper-contaminated mine sites.

Enhanced anti-bacterial properties and thermal regulation via photothermal conversion with localized surface plasmon resonance effect in cotton fabrics

Enhanced anti-bacterial properties and thermal regulation are realized in cotton fabrics cross-linked with hybrid poly(di(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate-co-ethylene glycol methacrylate) nanogels containing gold nanoparticles (Au NPs), denoted as hybrid P(MA-co-MA300-co-EGMA)/Au nanogels. Pure P(MA-co-MA300-co-EGMA) nanogels are synthesized by emulsion polymerization as carriers and then embedded with Au NPs via in-situ reduction. By applying 1,2,3,4-butanetetracarboxylic acid as a cross-linker and changing the amount of hybrid P(MA-co-MA300-co-EGMA)/Au nanogels in solution, the weight gain ratios of hybrid nanogels on cotton fabrics are set as 10 % (CHN-10) and 20 % (CHN-20). Due to the densely packed structure of the hybrid nanogels on the surface, the localized surface plasmon resonance (LSPR) effect of the Au NPs improves the photothermal conversion capability and converts the absorbed light energy into thermal energy. Simply illuminating with visible light, the surface temperature of CHN-20 pronouncedly increases from 20.4 to 43.0 °C in 50 s. The increased local temperature induces the denaturation of protein and the death of bacteria on the surface. Thus, an illumination with visible light for 2 h results in an anti-bacterial rate for S. aureus of 100 % for CHN-20. Additionally, it presents an excellent thermal regulation capability via photothermal conversion and can be used for continuously maintaining human body temperature in cold areas. Because no additional chemical agents and external power source are required for the anti-bacterial properties and thermal regulation, the obtained cotton fabrics cross-linked with hybrid P(MA-co-MA300-co-EGMA)/Au nanogels are eco-friendly and suitable for smart textiles in daily wear.

Effect of nano‐silica on the mechanical performance and porosity evolution of concrete under freezing and thawing cycles

AbstractThe enhancement of freeze–thaw resistance in concrete is crucial for improving the durability and longevity of infrastructure in cold regions. Although the benefits of nano‐silica (NS) on concrete's freeze–thaw resistance have been demonstrated, there is still controversy surrounding the optimal concentration of admixture and underlying mechanisms. In this study, the mechanical performance (mass weight, elastic modulus, compressive and splitting strength) and porosity evolution (total porosity, porosity distribution and micro‐surface morphologies) of control concrete and concrete modified with five different NS admixture concentration (1%–5%) were tested under freezing and thawing (F–T) cycles, and damage models were established to assess the correlations between macroscopic and microscopic damages. The results indicate that F–T cycles lead to both damage in mechanic properties and porosity in concrete specimens. The effects of NS particles on macroscopic and microscopic damage under F–T conditions depend on their admixture concentration. A 2% concentration mitigates while a 5% dosage promotes both macroscopic and microscopic damages during F–T cycles. These differences can primarily be attributed to different dispersion status of NS particles in concrete, leading to variations in porosity evolution during F–T cycles. The macroscopic damage exhibit stronger correlation with microscopic damage factor modified by proportion of large pores compared to that only based on total porosity, suggest that the microscopic damage, especially large pores' proportion, contribute to macroscopic damage of concrete specimens under F–T cycles. These findings provide valuable references for field concrete engineering applications in cold areas.

Cropping and Pruning Systems of Primocane Raspberries in the Subtropical Climate

Raspberry production is limited to cold temperate areas of high latitude due to the requirement of low temperatures for flowering and fruiting from most cultivars. However, primocane cultivars, as they are less demanding in cold conditions, represent a possible alternative that suits regions with a subtropical climate. The cultivar Heritage primocane raspberry was investigated in the Cwa climate, in three production systems (PS), during two crop cycles. In PS1, canes were hard pruned at ground level after primocane fruiting. In PS2, canes were tipped to promote subapical bud break for a second harvest. In PS3, canes were tipped again after the second harvest to induce a third harvest. PS1 had the lowest yield, however, after two cycles; in plants of this system it was observed the highest root weight, and starch content. Raspberries subjected to subapical pruning show lower carbohydrate storage in the root system. The production systems had little influence on fruit qualities, in both cycles. The cultivation of cv. Heritage raspberry primocane, in the subtropical Cwa climate can be carried out with sequential pruning, allowing for the production of commercial fruits with harvests distributed over the months, without any reduction in the postharvest quality of the fruits produced.

Analytical study on plastic loosening zone of weak surrounding rocks tunnel in high cold areas

AbstractThe analysis of plastic loosening zone of tunnels with cold condition, high in situ stress, and weak stratum is the key scientific problem of tunnel construction in cold areas. Based on the unified strength theory and considering the coupling effect of high in situ stress and low‐temperature field, the analytical model of the plastic loosening zone of tunnel surrounding rocks was proposed, and the influence laws of physical parameters (initial ground stress, freezing temperature, excavation radius, and intermediate principal stress) was explored. The results illustrate that: (1) with the coupling of low temperature and stress fields, the in‐situ stress has a more significant effect on the radius of the plastic loosening zone of the tunnel surrounding rocks, showing a nonlinear correlation. When the in situ stress is small, the influence of the temperature field on the radius of the plastic loosening zone is more obvious. (2) The radius of the plastic loosening zone of the tunnel surrounding rocks increases synchronously with the excavation radius and gradually decreases with the increase of the intermediate principal stress. (3) The greater the temperature difference in the low‐temperature field, the tunnel stability has a more significant response to the intermediate principal stress and is positively correlated with the coefficient of the intermediate principal stress. (4) In the actual project, the proposed model can well describe the mechanical behavior and deformation characteristics of tunnel surrounding rocks in low‐temperature environment, showing applicability. The research results are expected to provide a theoretical basis for the study of tunnel stability in cold areas.

Exergy-economic based multi-objective optimization and carbon footprint analysis of solar thermal refrigeration systems

The increasing carbon footprint associated with conventional cooling methods underscores the urgent need for sustainable alternatives. This study investigates the economic and environmental advantages of various solar-thermal cooling systems, with a focus on optimizing their performance across different climate conditions. Employing a multi-objective approach, the research emphasizes exergy-economic indices to optimize selected cycles. The analysis covers multiple refrigeration technologies, including liquid absorption, solid adsorption, and solid desiccant cycles. Results indicate that the liquid absorption cycle performs optimally in hot, arid climates, reducing the payback period to approximately 8 years when optimized. In hot and humid regions, the solid desiccant cycle proves most effective due to its superior humidity control, yielding a payback period of 5.3 years. For cold and mountainous areas, the solid adsorption cycle is preferred, with a payback period of 13.5 years, while moderate and humid climates benefit from the solid desiccant cycle for both cooling and humidity regulation. The exergy-economic factors for the solar refrigeration systems across semi-arid, hot and arid, hot and humid, cold and mountainous, and moderate and humid climates are 0.758, 0.602, 0.698, 0.74, and 0.575, respectively.

Improved volatile fatty acid production in anaerobic digestion via simultaneous temperature regulation and persulfate activation by biochar: Chemical and biological response mechanisms

Increasing volatile fatty acid (VFA) production via persulfate activation (i.e., chemical effect) in anaerobic digestion (AD) is an emerging resource utilization method. However, the reaction mechanisms responsible for improving VFA production in AD via simultaneous temperature regulation and persulfate activation by biochar remain unclear. In this study, three PB15 treatment systems of low temperature (15 °C), medium temperature (35 °C) and high temperature (55 °C) were set to explore the relationship between VFAs production and treatment temperature and the influence of temperature on the reaction mechanism. The results show that the improvement of hydrolysis and acidification efficiency of the system in the medium temperature system is the highest. The VFA yield and acid production rate in the treatment group at 35 °C were 2.49 and 5.22 times higher than those in the control group, respectively. The chemical effect effectively initiated the anaerobic acid production process and maintained the dominant role of the biological effect. The activity of persulfate is too low at low temperature, and its decomposition is too fast at high temperature. Plenty of free radicals lead to enhanced oxidation of the system, which may kill the fermentation bacteria. The NCM model indicates that microbial stability is reduced in high temperature systems. The SEM model showed that temperature change mainly affected substrate degradation by hydrolytic bacteria and indirectly affected acid production by acid-producing bacteria. This study provides a new strategy for realizing pollutant recycling and increasing VFAs production in cold area.

Unified elastoplastic solution for the stress and displacement of tunnel lining and surrounding rock in cold areas considering heterogeneous characteristics

The lining and surrounding rock around tunnels constructed in cold areas exhibit nonuniform material properties due to the existence of a temperature field. This study considered the effects of these properties on the integrity of tunnel structures. By establishing an elastoplastic mechanical model, analytical solutions to the stress and displacement under five different elastoplastic states were derived and compared based on distinct yield criteria. The findings showed that with increasing relative radius, the displacement in the lining elastic zone initially decreased before increasing, whereas the shift in the plastic zone continued to increase. The displacement in the elastic zone of the frozen surrounding rock intensified with increasing relative radius, whereas the shift in the plastic zone experienced a gradual decline. The displacement of the inner wall of the lining was always greater than that of the outer wall, and this phenomenon occurred only after the frozen surrounding rock exhibited a plastic zone. The maximum displacements of the liner in its elastically limited and plastically limited states were 1.39, 1.77, 2.28, and 2.37 ​mm and 15.93, 25.51, 44.28, and 48.58 ​mm based on the Drucker–Prager (DP), Mohr–Coulomb (MC), Tresca, and double-shear strength criteria, respectively; the maximum limit displacements of the frozen surrounding rock were 12.74, 20.41, 35.43, and 38.87 ​mm and 85.32, 103.38, 569.23, and 680.43 ​mm, respectively. With increasing relative radius, the radial stresses within both the lining and the frozen surrounding rock intensified; and the tangential stress in the elastic zone of the lining decreased whereas the opposite change rule was observed in the plastic zone. The tangential stresses in the frozen surrounding rock and lining exhibited the same variation trend. Based on calculations with four distinct strength criteria, the elastic and plastic ultimate bearing capacities of the lining were 1.81, 2.31, 2.95, and 3.07 ​MPa, and 3.31, 4.84, 7.48, and 8.05 ​MPa, while those of the frozen surrounding rock were 8.52, 13.24, 22.17, and 24.18 ​MPa, and 16.76, 32.46, 74.15, and 85.64 ​MPa. In addition, with the expansion of the plastic zone, the phenomenon of a sudden change in the tangential stress at location r2 became progressively attenuated. The study findings can provide some theoretical guidance for the design and construction of tunnels in cold areas.

Growing-degree-days (GDDs) in a uniform phenology scale (BBCH) for two walnut (Juglans regia L.) cultivars

ABSTRACT Descriptors are widely used for monitoring the phenology and pomology of plants. Among them, the BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) scale is the most important. We evaluated the growth of ‘Chandler’ and ‘Persia’ walnut cultivars to create a BBCH descriptor for the crop, and estimate the growing-degree days (GDDs) of different growth stages. The GDDs (°C-days) were measured using 0°C as a base temperature (Tb) for male flowering and 5.5°C for other phenological stages in both cultivars. Growth stages were divided into eight principal stages, each with multiple substages. Stage 0 includes the bud sprouting, while stage 9 occurs when the leaves develop and the tree enters the dormancy. Both cultivars had a similar heat unit requirement at the bud quiescent stage (84 and 71°C-days for ‘Chandler’ and ‘Persia’, respectively); however, ‘Chandler’ needs higher GDDs accumulation to reach the harvest (3876°C-days compared to 3539°C-days for ‘Persia’). The results suggest that ‘Persia’ can be cultivated in colder areas at higher altitudes or latitudes compared with ‘Chandler’.

Effectiveness and Risk Assessment of Septic Tank Treatment Systems in Rural Cold Regions of China

Rural toilet reform in cold areas is the focus and difficulty of China’s toilet revolution. In this paper, by carrying out the septic tank gradient burial depth test and regular seasonal monitoring of the operation effect of rural septic tanks in cold areas, the frost protection effect and treatment effect of rural toilets in cold areas are clarified, which provide important references for the rural toilet revolution and its practical significance in cold areas of China. Based on controlled tests and correlation analysis methods, different gradient burial depths of septic tanks (40, 60, and 80 cm) and different seasonal operation effects (spring, summer, autumn, and winter) were studied to analyze the influence of factors such as burial depths and temperatures on the effectiveness of anti-freezing and treatment of septic tanks. The results found that the septic tank effluent indexes of the six cold-zone test households could not meet requirements of Class Ⅰ-B in the discharge standard of pollutants for municipal wastewater treatment plants (GB 18918-2002). (The criteria for Class I-B are as follows: COD emission limit of 60 mg/L; SS emission limit of 20 mg/L; TN emission limit of 20 mg/L; TP emission limit of 1 mg/L; NH3-N emission limit of 8 mg/L); The average removal of suspended solids (SSs), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), NH3-N, and NO3-N by septic tanks was 79.7%, 21.8%, 10.5%, 13.5%, 9.76%, and 2.38%, respectively; the water temperature was significantly positively correlated with SS, TN, and TP; the double-layer insulated septic tank with medium burial depth (60 cm) could operate normally in cold areas in winter. The treatment effect of septic tanks on various indicators basically shows that summer > autumn > spring > winter. Temperature is the main limiting factor affecting the treatment effect of septic tanks.

A Model that Explains the Contrasting SST Trends in the Southern Pacific Ocean

Sea surface temperature (SST) of the southern Pacific Ocean plays an important role in ocean-atmospheric interactions, influencing both regional and global climate and ecosystems. The contrasting SST trends in the southern Pacific Ocean during 1993-2021 are noted by analyzing satellite and in-situ datasets, consisting of SST warming trend (0.05℃·yr−1) in the region of 80°W-180,30°S-50°S and cooling trend (−0.04℃·yr−1) in the area of 60°W-150°W, 55°S-70°S. A detailed trend analysis for the wind and sea ice concentration suggest that Ekman transport and sea ice radiative positive feedback are the two key contributors to the contrasting SST trends. The intensified downwelling (upwelling), induced by the Ekman transport and strengthened westerlies, gives rise to warm (cold) water swarming in (upturning) from lower latitudes (deeper ocean), which causes SST warming (cooling). Moreover, the sea ice increase at higher latitudes, due to both the cold water transport from deeper ocean layers and broken ice transport from polar regions, strengthens the cooling trend through sea ice positive radiative feedback. In conclusion, these findings underscore the complexity of SST trends in the southern Pacific Ocean, highlighting the critical roles of Ekman transport and sea ice radiative feedback in shaping regional climate dynamics.Plain Language Summary: The southern Pacific Ocean is an indispensable part in the climate system while it still remained poorly observed. The SST trend is regarded as a critical indicator of global climate change. Using the satellite and in-situ datasets, we find that the contrasting SST trends from 1993 to 2021, one area in this region is warmed by 0.3℃ per decade, while another area is cooled by -0.1℃ per decade. Considering impacts of various factors such as wind, sea ice and radiation, the primarily explanation is that wind-driven warm (cold) water from the subtropics (deeper ocean) flows in and goes downward (goes upward and flow away) in the warm (cold) area through oceanic circulation and leads to the SST warming (cooling). Additionally, the cooling trend is also related to the cold water that flows to higher latitudes and forms ice there and at the same time, trash ice from polar regions driven by enhanced south wind speed will be transported there. As a result, ice increases, reflects more shortwave radiation to space, and surface downward shortwave radiation decreases which contributes to SST decreases.

Experimental Study on Mechanical Characteristics of Stabilized Soil with Rice Husk Carbon and Calcium Lignosulfonate.

In cold regions, the extensive distribution of silt exhibits limited applicability in engineering under freeze-thaw cycles. To address this issue, this study employed rice husk carbon and calcium lignosulfonate to stabilize silt from cold areas. The mechanical properties of the stabilized silt under freeze-thaw conditions were evaluated through unconfined compressive strength tests and triaxial shear tests. Additionally, scanning electron microscopy was utilized to analyze the mechanisms behind the stabilization. Ultimately, a damage model for rice husk carbon-calcium lignosulfonate stabilized silt was constructed based on the Weibull distribution function and Lemaitre's principle of equivalent strain. The findings indicate that as the content of rice husk carbon and calcium lignosulfonate increases, the rate of improvement in the compressive strength of the stabilized silt progressively accelerates. With an increase in the number of freeze-thaw cycles, the deviatoric stress of the stabilized soil gradually diminishes; the decline in peak deviatoric stress becomes more gradual, while the reduction in cohesion intensifies. The decrease in the angle of internal friction is relatively minor. Microscopic examinations reveal that as the number of freeze-thaw cycles increases, the soil pores tend to enlarge and multiply. The established damage model for stabilized silt under freeze-thaw cycles and applied loads demonstrates a similar pattern between the experimental and theoretical curves under four different confining pressures, reflecting an initial rapid increase followed by a steady trend. Thus, it is evident that the damage model for stabilized silt under freeze-thaw conditions outperforms traditional constitutive models, offering a more accurate depiction of the experimental variations observed.

Improvement of Saline–Alkali Soil and Straw Degradation Efficiency in Cold and Arid Areas Using Klebsiella sp. and Pseudomonas sp.

Corn straw is an important renewable resource, which could improve the quality of saline–alkali cultivated land. However, the slow decomposition of crop residues in cold, arid, and saline–alkali soils can lead to serious resource waste and ecological crises. The use of beneficial microorganisms with degradation functions could solve these problems. In this study, three types of saline–alkali soil with low, medium, and high salinity levels were used in the straw-returning experiment. The experiment was conducted with four treatments: GF2 (Klebsiella sp.), GF7 (Pseudomonas sp.), GF2+GF7, and CK (control without bacteria). Microbial characteristics, straw degradation efficiency, element release rate, and soil factors were compared, and random forest linear regression and partial least squares path modeling analysis methods were utilized. The results indicated that the degradation of bacterial metabolites, the efficiency of corn stover degradation, the efficiency of component degradation, and the release rates of elements (C, N, P, and K) initially increased and then decreased with the increase in salinity. At the maximum value of moderately saline–alkali soil, the effect of GF2+GF7 treatment was significantly better than that of other treatments (p < 0.05). Given the interactive effects of saline–alkali soil and microbial factors, the application of exogenous degrading bacteria could significantly increase soil enzyme activity and soil available nutrients, as well as regulate the salt–alkali ion balance in soil. The cation exchange capacity (9.13%, p < 0.01) was the primary driving force for the degradation rate of straw in saline–alkali soil with different degrees of salinization under the influence of exogenous degrading bacteria. Straw decomposition directly affected the soil chemical properties and indirectly affected soil enzyme activity. The results of this study would provide new strategies and insights into the utilization of microbial resources to promote straw degradation.

Potato growth, nitrogen balance, quality, and productivity response to water-nitrogen regulation in a cold and arid environment.

The pervasively imprudent practices of irrigation and nitrogen (N) application within Oasis Cool Irrigation zones have led to significant soil nitrogen loss and a marked decrease in water and nitrogen use efficiency. To address this concern, a comprehensive field experiment was conducted from April to September in 2023 to investigate the impact of varying degrees of water and fertilization regulation strategies on pivotal parameters including potato yield, quality, nitrogen balance, and water-nitrogen use efficiency. The experimental design incorporated two water deficit degrees at potato seedling (W1, 55%-65% of Field Capacity (FC); W2, 45%-55% of FC), and four distinct nitrogen application gradients (N0, 0 kg ha-1 of N; N1, 130 kg ha-1 of N; N2, 185 kg ha-1 of N; N3, 240 kg ha-1 of N). A control was also included, comprising N0 nitrogen application and full irrigation (W0, 65%-75% of FC), totally eight treatments and one check. The results indicated that the tuber yield, plant dry matter accumulation, plant height, plant stem, and leaf area index increased with higher nitrogen fertilizer application and irrigation volume. However, tuber starch content, vitamin C, and protein content initially increased and then decreased, while reducing sugar content consistently decreased. Except for W1N2 treatment, the irrigation water use efficiency increased as the N application rate rose, while the nitrogen partial factor productivity, crop nitrogen use efficiency and soil nitrogen use efficiency decreased with an increase in N fertilizer application. The W1N2 treatment resulted in a higher yield (43.16 t ha-1), highest crop nitrogen use efficiency (0.95) and systematic nitrogen use efficiency (0.72),while maintaining moderate levels of soil nitrate and ammonium nitrogen. Therefore, through the construction of an integrated evaluation index (IEI), the W1N2 treatment of mild water deficit (55%-65% of FC) at potato seedling combined with the medium nitrogen application (185 kg ha-1 of N) has the highest IEI (0.978), it was recommended as the optimal water-nitrogen regulation and management strategies to facilitate high-yield, high-efficiency, and environmentally sustainable potato production in the cold and arid oasis areas of northwest China.